1. Field of the Invention
The present invention relates to a scanner control method, a scanner, a duplicate printer, a mediating device, and a storage medium. More particularly, the present invention is concerned with a scanner control method, a scanner, a duplicate printer, a mediating device, and a storage medium, premising the use in an environment in which the printer is connected to the scanner, the scanner having a line-like photoelectric transducer which reads an original image by photoelectric conversion, the printer having a relatively lower write speed than the read speed of the line-like photoelectric transducer.
2. Description of the Prior Art
Generally, a copying machine is used for duplicating an original image. Particularly, with the recent development of digital technique, digital copying machines have become more and more popular.
As shown in FIG. 1, a digital copying machine is roughly composed of a scanner 2 constituted mainly by a read unit 1, an image processing unit 3, and a printer 5 constituted mainly by a write unit 4. The read unit 1 is provided with one-dimensional array-like CCDs 6 used commonly as line-like photoelectric transducers which read an original image by making photoelectric conversion on the basis of reflected light from an exposure-lighted original. The image processing unit 3 is provided in the scanner 2 or in the printer 5 and performs an image processing for the read original image. For example, the image processing unit 3 is provided with a black offset correction circuit 7, a shading correction circuit 8, an image magnification varying circuit 9, a filter circuit 10, an image quality processing circuit 11, a video pass circuit 12, a test pattern generating circuit 13, a command register 14, a memory 15, an I/F control circuit 16. The printer 5 forms an electrostatic latent image on a photosensitive member in accordance with an electrophotographic process, develops the latent image, and thereafter transfers the resulting visible image onto a transfer paper. The write unit 4 is provided with a light source such as a semiconductor laser (LD) or an LED for writing onto the photosensitive member and is also provided with a drive unit 17 for driving the writing light source (LD or LED).
Such a digital copying machine is becoming higher and higher in its processing speed. For example, the read cycle of the CCDs 6 in the scanner 2 and the write cycle in the write unit 4 are both several hundred microseconds per line (this is also the case with the processing cycle in the image processing unit 3). Thus, the writing process in one line may be executed while the reading process in one line is executed, by using FIFO (First In First Out) memory, so that the reading process and the writing process can be executed in parallel.
On the other hand, when an original image is to be duplicated and when the number of sheets to be duplicated (printed) is large, a stencil printer is advantageous and therefore a digital printer capable of duplicate-printing an original image is also available. Also in such a digital printer, for example in the case of a thermal stencil printer, as shown in FIG. 2, it is basically composed of a scanner 22 constituted mainly by a read unit 21, an image processing unit 23, and a printer 25 constituted mainly by a write unit 24. The scanner 22 and the image processing unit 23 are the same as in the digital copying machine, but as to the write unit 24 in the printer 25, it is greatly different from the digital copying machine in that it uses a thermal head as a process write head for stencil sheet, and it is provided with a thermal head driving unit 26 for driving the thermal head. The process write speed cannot be made such high as in the write processing in the electrophotographic process and actually the write cycle in the write unit 24 is considered to be about several milliseconds per line.
Problems involved in such prior art will now be described. In the digital printer, because of a different write-side processing speed (write cycle) even in spite of the same original image reading and image processing, a dedicated scanner 22 is designed so as to give a read cycle by CCDs 27 of several milliseconds or so per line also on the read unit 21 side.
That is, the high-speed scanner 2 for a digital copying machine, which is available widely, cannot be shared by digital printers; in other words, in producing a digital printer, it is necessary to develop a dedicated scanner 22, which results in an increase of the development cost.
Practical use of an interface like USB enables a scanner connected with a network to use as a network scanner. Accordingly, it is supposed that the writing process using CCDs in one line is executed while the reading process in one line is executed, by using FIFO (First In First Out) memory, so that the reading process and the writing process is executed in parallel. However, reading speed of the scanner and writing speed of the printing device are not equal, so that the above problem will occur.